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Water Storage Pond Compacted Clay Liner Parcel 1, 8%, 5W'/a, Section 35, T1$, R67W Adams County, Colorado CLAY LINER SYSTEM Based on the testing performed for GROUND's November 8, 2002, report, claystone material excavated from the project area appears suitable for use as pond liner. The data Indicated that the local claystone-derived material generally falls within the parameters specified by the State of Colorado regarding plasticity and gradation (Division of Mines and Geology, 2000). A measured hydraulic conductivity value of 1.4 X 10"7 cm/s was below the maximum hydraulic conductivity allowed by the State Engineer's office for such material (1 x 10-6 cm/s). Therefore, GROUND recommends that on-site claystone material, free of deleterious materials or more than scattered sandstone fragments, be used to construct the proposed pond liner. GROUND recommends that the compacted clay liner be at least 15 feet in horizontal thickness. Placed on a 2: 1 (horizontal : vertical) this will result in a finer that is 7.5 feet in vertical thickness. GROUND also recommends that the clay liner be covered with 'miscellaneous fill' consisting of granular, on-site soils. In accordance with the Division of Mines and Geology (2000), GROUND recommends that the proposed liner be keyed into the underlying bedrock. The keyway should be at least 4 feet in depth and 4 or more feet in width. In addition, as the fill is placed, it should be benched into the existing slope and placed in relatively horizontal lifts. Benching should be accomplished by excavating into the existing slope a minimum of 3 feet horizontally for each bench (maximum of 2 feet vertically). The excavated claystone materials should be thoroughly mixed to achieve a uniform moisture content, placed in uniform lifts not exceeding 8 inches in loose thickness, and compacted to at least 95 percent of the maximum standard Proctor density at moisture contents from optimum to 4 percent above the optimum as determined by ASTM D698. We anticipate that these soils may exhibit significant pumping, rutting, and deflection at moisture contents near optimum and above. The contractor should be prepared to work with these plastic clay soils. Excavated claystone will require a well-coordinated effort to moisture treat, process, place and compact property. In-place claystone deposits were dense and relatively dry, and require a significant volume of water to be mixed into the excavated material to bring it to a uniform moisture content from optimum to 4 percent above the optimum prior to compaction. Job No. 09-3090 GROUND Engineering Consultants, Inc. Page 4